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ref:cde9a383711a11544ce7e107a78147fb96cc4029

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diff --git a/contrib/libs/llvm12/include/llvm/ADT/PostOrderIterator.h b/contrib/libs/llvm12/include/llvm/ADT/PostOrderIterator.h
new file mode 100644
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+++ b/contrib/libs/llvm12/include/llvm/ADT/PostOrderIterator.h
@@ -0,0 +1,323 @@
+#pragma once
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
+//===- llvm/ADT/PostOrderIterator.h - PostOrder iterator --------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file builds on the ADT/GraphTraits.h file to build a generic graph
+// post order iterator.  This should work over any graph type that has a
+// GraphTraits specialization.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_POSTORDERITERATOR_H
+#define LLVM_ADT_POSTORDERITERATOR_H
+
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/iterator_range.h"
+#include <iterator>
+#include <set>
+#include <utility>
+#include <vector>
+
+namespace llvm {
+
+// The po_iterator_storage template provides access to the set of already
+// visited nodes during the po_iterator's depth-first traversal.
+//
+// The default implementation simply contains a set of visited nodes, while
+// the External=true version uses a reference to an external set.
+//
+// It is possible to prune the depth-first traversal in several ways:
+//
+// - When providing an external set that already contains some graph nodes,
+//   those nodes won't be visited again. This is useful for restarting a
+//   post-order traversal on a graph with nodes that aren't dominated by a
+//   single node.
+//
+// - By providing a custom SetType class, unwanted graph nodes can be excluded
+//   by having the insert() function return false. This could for example
+//   confine a CFG traversal to blocks in a specific loop.
+//
+// - Finally, by specializing the po_iterator_storage template itself, graph
+//   edges can be pruned by returning false in the insertEdge() function. This
+//   could be used to remove loop back-edges from the CFG seen by po_iterator.
+//
+// A specialized po_iterator_storage class can observe both the pre-order and
+// the post-order. The insertEdge() function is called in a pre-order, while
+// the finishPostorder() function is called just before the po_iterator moves
+// on to the next node.
+
+/// Default po_iterator_storage implementation with an internal set object.
+template<class SetType, bool External>
+class po_iterator_storage {
+  SetType Visited;
+
+public:
+  // Return true if edge destination should be visited.
+  template <typename NodeRef>
+  bool insertEdge(Optional<NodeRef> From, NodeRef To) {
+    return Visited.insert(To).second;
+  }
+
+  // Called after all children of BB have been visited.
+  template <typename NodeRef> void finishPostorder(NodeRef BB) {}
+};
+
+/// Specialization of po_iterator_storage that references an external set.
+template<class SetType>
+class po_iterator_storage<SetType, true> {
+  SetType &Visited;
+
+public:
+  po_iterator_storage(SetType &VSet) : Visited(VSet) {}
+  po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
+
+  // Return true if edge destination should be visited, called with From = 0 for
+  // the root node.
+  // Graph edges can be pruned by specializing this function.
+  template <class NodeRef> bool insertEdge(Optional<NodeRef> From, NodeRef To) {
+    return Visited.insert(To).second;
+  }
+
+  // Called after all children of BB have been visited.
+  template <class NodeRef> void finishPostorder(NodeRef BB) {}
+};
+
+template <class GraphT,
+          class SetType =
+              SmallPtrSet<typename GraphTraits<GraphT>::NodeRef, 8>,
+          bool ExtStorage = false, class GT = GraphTraits<GraphT>>
+class po_iterator
+    : public std::iterator<std::forward_iterator_tag, typename GT::NodeRef>,
+      public po_iterator_storage<SetType, ExtStorage> {
+  using super = std::iterator<std::forward_iterator_tag, typename GT::NodeRef>;
+  using NodeRef = typename GT::NodeRef;
+  using ChildItTy = typename GT::ChildIteratorType;
+
+  // VisitStack - Used to maintain the ordering.  Top = current block
+  // First element is basic block pointer, second is the 'next child' to visit
+  SmallVector<std::pair<NodeRef, ChildItTy>, 8> VisitStack;
+
+  po_iterator(NodeRef BB) {
+    this->insertEdge(Optional<NodeRef>(), BB);
+    VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
+    traverseChild();
+  }
+
+  po_iterator() = default; // End is when stack is empty.
+
+  po_iterator(NodeRef BB, SetType &S)
+      : po_iterator_storage<SetType, ExtStorage>(S) {
+    if (this->insertEdge(Optional<NodeRef>(), BB)) {
+      VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
+      traverseChild();
+    }
+  }
+
+  po_iterator(SetType &S)
+      : po_iterator_storage<SetType, ExtStorage>(S) {
+  } // End is when stack is empty.
+
+  void traverseChild() {
+    while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
+      NodeRef BB = *VisitStack.back().second++;
+      if (this->insertEdge(Optional<NodeRef>(VisitStack.back().first), BB)) {
+        // If the block is not visited...
+        VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
+      }
+    }
+  }
+
+public:
+  using pointer = typename super::pointer;
+
+  // Provide static "constructors"...
+  static po_iterator begin(GraphT G) {
+    return po_iterator(GT::getEntryNode(G));
+  }
+  static po_iterator end(GraphT G) { return po_iterator(); }
+
+  static po_iterator begin(GraphT G, SetType &S) {
+    return po_iterator(GT::getEntryNode(G), S);
+  }
+  static po_iterator end(GraphT G, SetType &S) { return po_iterator(S); }
+
+  bool operator==(const po_iterator &x) const {
+    return VisitStack == x.VisitStack;
+  }
+  bool operator!=(const po_iterator &x) const { return !(*this == x); }
+
+  const NodeRef &operator*() const { return VisitStack.back().first; }
+
+  // This is a nonstandard operator-> that dereferences the pointer an extra
+  // time... so that you can actually call methods ON the BasicBlock, because
+  // the contained type is a pointer.  This allows BBIt->getTerminator() f.e.
+  //
+  NodeRef operator->() const { return **this; }
+
+  po_iterator &operator++() { // Preincrement
+    this->finishPostorder(VisitStack.back().first);
+    VisitStack.pop_back();
+    if (!VisitStack.empty())
+      traverseChild();
+    return *this;
+  }
+
+  po_iterator operator++(int) { // Postincrement
+    po_iterator tmp = *this;
+    ++*this;
+    return tmp;
+  }
+};
+
+// Provide global constructors that automatically figure out correct types...
+//
+template <class T>
+po_iterator<T> po_begin(const T &G) { return po_iterator<T>::begin(G); }
+template <class T>
+po_iterator<T> po_end  (const T &G) { return po_iterator<T>::end(G); }
+
+template <class T> iterator_range<po_iterator<T>> post_order(const T &G) {
+  return make_range(po_begin(G), po_end(G));
+}
+
+// Provide global definitions of external postorder iterators...
+template <class T, class SetType = std::set<typename GraphTraits<T>::NodeRef>>
+struct po_ext_iterator : public po_iterator<T, SetType, true> {
+  po_ext_iterator(const po_iterator<T, SetType, true> &V) :
+  po_iterator<T, SetType, true>(V) {}
+};
+
+template<class T, class SetType>
+po_ext_iterator<T, SetType> po_ext_begin(T G, SetType &S) {
+  return po_ext_iterator<T, SetType>::begin(G, S);
+}
+
+template<class T, class SetType>
+po_ext_iterator<T, SetType> po_ext_end(T G, SetType &S) {
+  return po_ext_iterator<T, SetType>::end(G, S);
+}
+
+template <class T, class SetType>
+iterator_range<po_ext_iterator<T, SetType>> post_order_ext(const T &G, SetType &S) {
+  return make_range(po_ext_begin(G, S), po_ext_end(G, S));
+}
+
+// Provide global definitions of inverse post order iterators...
+template <class T, class SetType = std::set<typename GraphTraits<T>::NodeRef>,
+          bool External = false>
+struct ipo_iterator : public po_iterator<Inverse<T>, SetType, External> {
+  ipo_iterator(const po_iterator<Inverse<T>, SetType, External> &V) :
+     po_iterator<Inverse<T>, SetType, External> (V) {}
+};
+
+template <class T>
+ipo_iterator<T> ipo_begin(const T &G) {
+  return ipo_iterator<T>::begin(G);
+}
+
+template <class T>
+ipo_iterator<T> ipo_end(const T &G){
+  return ipo_iterator<T>::end(G);
+}
+
+template <class T>
+iterator_range<ipo_iterator<T>> inverse_post_order(const T &G) {
+  return make_range(ipo_begin(G), ipo_end(G));
+}
+
+// Provide global definitions of external inverse postorder iterators...
+template <class T, class SetType = std::set<typename GraphTraits<T>::NodeRef>>
+struct ipo_ext_iterator : public ipo_iterator<T, SetType, true> {
+  ipo_ext_iterator(const ipo_iterator<T, SetType, true> &V) :
+    ipo_iterator<T, SetType, true>(V) {}
+  ipo_ext_iterator(const po_iterator<Inverse<T>, SetType, true> &V) :
+    ipo_iterator<T, SetType, true>(V) {}
+};
+
+template <class T, class SetType>
+ipo_ext_iterator<T, SetType> ipo_ext_begin(const T &G, SetType &S) {
+  return ipo_ext_iterator<T, SetType>::begin(G, S);
+}
+
+template <class T, class SetType>
+ipo_ext_iterator<T, SetType> ipo_ext_end(const T &G, SetType &S) {
+  return ipo_ext_iterator<T, SetType>::end(G, S);
+}
+
+template <class T, class SetType>
+iterator_range<ipo_ext_iterator<T, SetType>>
+inverse_post_order_ext(const T &G, SetType &S) {
+  return make_range(ipo_ext_begin(G, S), ipo_ext_end(G, S));
+}
+
+//===--------------------------------------------------------------------===//
+// Reverse Post Order CFG iterator code
+//===--------------------------------------------------------------------===//
+//
+// This is used to visit basic blocks in a method in reverse post order.  This
+// class is awkward to use because I don't know a good incremental algorithm to
+// computer RPO from a graph.  Because of this, the construction of the
+// ReversePostOrderTraversal object is expensive (it must walk the entire graph
+// with a postorder iterator to build the data structures).  The moral of this
+// story is: Don't create more ReversePostOrderTraversal classes than necessary.
+//
+// Because it does the traversal in its constructor, it won't invalidate when
+// BasicBlocks are removed, *but* it may contain erased blocks. Some places
+// rely on this behavior (i.e. GVN).
+//
+// This class should be used like this:
+// {
+//   ReversePostOrderTraversal<Function*> RPOT(FuncPtr); // Expensive to create
+//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
+//      ...
+//   }
+//   for (rpo_iterator I = RPOT.begin(); I != RPOT.end(); ++I) {
+//      ...
+//   }
+// }
+//
+
+template<class GraphT, class GT = GraphTraits<GraphT>>
+class ReversePostOrderTraversal {
+  using NodeRef = typename GT::NodeRef;
+
+  std::vector<NodeRef> Blocks; // Block list in normal PO order
+
+  void Initialize(NodeRef BB) {
+    std::copy(po_begin(BB), po_end(BB), std::back_inserter(Blocks));
+  }
+
+public:
+  using rpo_iterator = typename std::vector<NodeRef>::reverse_iterator;
+  using const_rpo_iterator = typename std::vector<NodeRef>::const_reverse_iterator;
+
+  ReversePostOrderTraversal(GraphT G) { Initialize(GT::getEntryNode(G)); }
+
+  // Because we want a reverse post order, use reverse iterators from the vector
+  rpo_iterator begin() { return Blocks.rbegin(); }
+  const_rpo_iterator begin() const { return Blocks.crbegin(); }
+  rpo_iterator end() { return Blocks.rend(); }
+  const_rpo_iterator end() const { return Blocks.crend(); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_POSTORDERITERATOR_H
+
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif